Different from the rigid separation of biological tissue by scalpel, medical waterjet technology utilizes the impact kinetic energy of high-speed waterjet to instantly destroy the surface of biological tissue to achieve better clinical separation effect. Since the gelatin samples are transparent biomaterials, they were taken as the only substitute for soft tissue in experimental studies and observation in the current studies of medical waterjet separation technology, but the mechanical behavioural difference between the two has not been reported. To verify the adaptability of gelatin as a substitute of soft tissue under the impact of high-speed waterjet. Firstly, the dynamic process of impact was described through the energy balance equation. Then, based on the principle of altering a single variable, the difference of damage depth between 8 wt. %, 10 wt. %, and 12 wt. % gelatin samples and porcine liver tissue under various impact pressure, impact distance, and waterjet speed of motion (as opposed to flow velocity) was compared. The results show that the gelatin sample replicates the damage behaviour of porcine liver samples under the specific waterjet impact conditions, and the direction of the waterjet hydraulic power optimisation of the two materials is also consistent: however, due to the different sampling sites and anisotropy of porcine liver samples, the mechanical response of soft tissue under high-speed waterjet impact cannot be fully expressed by gelatin samples. The experimental results can provide support for the further study of medical waterjet separation technology.

The hydraulic support liquid supply system provided power for the hydraulic support, serving as the core to ensure safe support of the coal mining face and to maintain continuous, efficient, and stable advancement of the coal mining operations. The hydraulic support faced complex loads while operating on the fully mechanized mining face. To meet the requirement of rapidly following the coal mining machine’s movement, numerous actuators of the hydraulic support frequently performed sequential actions, and the liquid demand of the hydraulic support varied strongly over time, causing the hydraulic system to endure constant pressure and flow shocks, making it difficult to ensure the production efficiency and equipment reliability of comprehensive working face. This study analyzed the pressure and flow characteristics of the liquid supply system during the periodic actions of the hydraulic support. To address the strong time-varying load and liquid demand during the simultaneous actions of the hydraulic support, an Extended State Observer (ESO) was designed for observation and compensation. An Active Disturbance Rejection Control (ADRC) method suitable for the configuration of a rapid pump-controlled liquid replenishment and pressure stabilization system was proposed, and a co-simulation model of the mechanical and control systems was developed by comparing indicators such as the pressure fluctuation amplitude and the execution time of the hydraulic support actions. The pressure stabilization control effects of the ADRC method, the PID control method, and the traditional multi-pump coordinated liquid supply mode under typical time-varying conditions were analyzed and compared. A simulation test system was constructed to validate the results, demonstrating that the ADRC rapid fluid replenishment and pressure stabilization control method can suppress load disturbances, reduce the system pressure fluctuation amplitude by 20.8%, and shorten the hydraulic support operation time by 2.6%.

The position straightness of the hydraulic supports is the key factor to the intelligent fully mechanized mining, and the adjacent cylinder is the actuator used to pull the hydraulic support. However, the control component of the adjacent cylinder is electromagnetic on/off valve that cannot control the movement of adjacent cylinder proportionally. Therefore, a novel proportional water flow valve with a digital pilot stage is proposed to control the trajectory of adjacent cylinder precisely. The novel valve consists of a dual active cartridge main valve and a digital pilot valve that includes a high speed on/off valve A (HSV-A) and a throttle valve piloted by the high speed on/off valve B (HV-B). A coupling dynamic mathematical model of the flow valve is formulated and the dynamic characteristics of the valve is analyzed theoretically. The fluctuation of the throttle valve and main spool motion is also analytically calculated. In addition, the influences of the control parameters and key structural parameters on the throttle valve and the main valve's motion are analyzed on the basis of AMESim simulation respectively. The simulation results have demonstrated that the displacement fluctuation of the valve can be reduced by increasing the control frequency. The throttle valve closed-loop displacement fluctuation is about 0.2 mm and 0.1 mm when the control frequency is 100 Hz and 200 Hz. What's more, decreasing the main valve orifice diameter can also effectively lower the main valve displacement fluctuation, while it will diminish the main valve response speed at the same time.

Accurate control of hydraulic support movement in coal mining remains a significant technical challenge due to the limitations of existing electro-hydraulic directional valves, which are typically on/off valves without proportional control function. To address this issue, a high-pressure, large-flow water hydraulic proportional flow valve piloted by two high speed on/off valves is proposed. The main valve spool employs a symmetrical cylinder type cone structure, featuring a non-full circle U-shaped valve port. The transfer function of the flow valve is derived based on Laplace transformation, and the impact of discrete pulse flow output from the high speed on/off valves on main valve displacement fluctuations is theoretically calculated. The influence of the key structural parameters and control parameters on the main valve dynamic characteristics is also simulated. Finally, a prototype of the flow valve is developed and a semi-physical simulation testing rig using Matlab/xPC Target is constructed. The experiment results demonstrate the flow valve exhibits favorable dynamic and static characteristics, with the step rise time of 0.3 s and the steady-state error of 0.18mm. The amplitude–frequency experiments reveal that the proposed flow valve achieves a frequency response of no less than 2 Hz at 100% full scale. The proposed flow valve is not limited to coal mining applications, and it is suitable for use in high-temperature and high-pressure heavy machinery equipment operating.